1. Field of the Invention
The invention generally involves implantable prosthetic devices capable of restoring normal functions to fractured or diseased bones such as the femur, tibia or humerus.
2. Description of Prior Art
Many artificial implanted devices are in use at the present to repair or replace damaged bones. Some of these implants are very simple means such as screws, rods and wires. More complex devices are used to replace certain bones constituting a joint. In many cases the major problem encountered was the difficulty in obtaining a long lasting, strong and secure mechanical connection between the bone and the prosthesis. Biomechanical events causing dislodgement or premature failure of the implants are chiefly the repetitively changing stresses within the prosthesis and the bone. Bonding the implant with cement serves only as a partial solution to this problem. Another important factor is that the live bone will show definite changes in its geometry, hardness and other properties as a function of time. These changes may adversely influence the originally established strength and security of the combined structure of the bond and the prosthesis. Another problem frequently encountered is an oversight in the design by, not recognizing fully the effects of stresses caused by dynamic loads applied to the prosthesis. Also, in many instances there is a dangerously high concentration of stresses confined to a relatively small area. These stresses are responsible for a great number of failures.